锂在负极材料中的扩散行为对其大倍率充放电性能的影响

Influence of diffusion of lithium in negative electrodes on their high rate performance

采用恒电位阶跃的方法,对锂在锂离子电池负极材料中的扩散系数进行测量,对天然石墨和中间相炭微球两种负极材料进行了大倍率充放电性能测试。结果表明,锂在两种负极材料中的扩散系数是不同的,锂在天然石墨中的扩散系数较小,只有1.90×10-11cm2/s,而锂中间相炭微球中的扩散系数较大,达4.25×10-9cm2/s,扩散系数大,电极的大电流充放电性能好,天然石墨在5 C放电下放电平台升高到0.3 V,放电容量急剧减小,而中间相炭微球在5 C放电下仍能保持0.2 V左右的放电平台,放电容量保持在234 mA.h/g。

The potential step method has been used for measuring the diffusion coefficient of lithium in nature graphite and mesocarbon microbeads （MCMBs）. And high rate charge-discharge was presented for the two different materials. The results showed that the diffusion coefficients of lithium in nature graphite and MCMBs are different. The former is 1.90×10^-11 cm^2/s and the latter is 4.25×10^-9 cm^2/s. The electrode with higher diffusion coefficient of lithium has better high current charge-discharge performance. The discharge capacity of nature graphite rapidly reduced and its discharge fiat raised to 0.3 V. MCMBs have discharge fiat of about 0.2 V and discharge capacity of 234 mA·h/g.